Provided by: libexplain-dev_1.4.D001-12_amd64 
NAME
explain_ptrace - explain ptrace(2) errors
SYNOPSIS
#include <libexplain/ptrace.h>
const char *explain_ptrace(int request, pid_t pid, void *addr, void *data);
const char *explain_errno_ptrace(int errnum, int request, pid_t pid, void *addr, void
*data);
void explain_message_ptrace(char *message, int message_size, int request, pid_t pid, void
*addr, void *data);
void explain_message_errno_ptrace(char *message, int message_size, int errnum, int
request, pid_t pid, void *addr, void *data);
DESCRIPTION
These functions may be used to obtain explanations for errors returned by the ptrace(2)
system call.
explain_ptrace
const char *explain_ptrace(int request, pid_t pid, void *addr, void *data);
The explain_ptrace function is used to obtain an explanation of an error returned by the
ptrace(2) system call. The least the message will contain is the value of strerror(errno),
but usually it will do much better, and indicate the underlying cause in more detail.
The errno global variable will be used to obtain the error value to be decoded.
request The original request, exactly as passed to the ptrace(2) system call.
pid The original pid, exactly as passed to the ptrace(2) system call.
addr The original addr, exactly as passed to the ptrace(2) system call.
data The original data, exactly as passed to the ptrace(2) system call.
Returns:
The message explaining the error. This message buffer is shared by all libexplain
functions which do not supply a buffer in their argument list. This will be
overwritten by the next call to any libexplain function which shares this buffer,
including other threads.
Note: This function is not thread safe, because it shares a return buffer across all
threads, and many other functions in this library.
Example: This function is intended to be used in a fashion similar to the following
example:
long result = ptrace(request, pid, addr, data);
if (result < 0)
{
fprintf(stderr, "%s\n", explain_ptrace(request, pid, addr, data));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_ptrace_or_die(3) function.
explain_errno_ptrace
const char *explain_errno_ptrace(int errnum, int request, pid_t pid, void *addr, void
*data);
The explain_errno_ptrace function is used to obtain an explanation of an error returned by
the ptrace(2) system call. The least the message will contain is the value of
strerror(errno), but usually it will do much better, and indicate the underlying cause in
more detail.
errnum The error value to be decoded, usually obtained from the errno global variable
just before this function is called. This is necessary if you need to call any
code between the system call to be explained and this function, because many libc
functions will alter the value of errno.
request The original request, exactly as passed to the ptrace(2) system call.
pid The original pid, exactly as passed to the ptrace(2) system call.
addr The original addr, exactly as passed to the ptrace(2) system call.
data The original data, exactly as passed to the ptrace(2) system call.
Returns:
The message explaining the error. This message buffer is shared by all libexplain
functions which do not supply a buffer in their argument list. This will be
overwritten by the next call to any libexplain function which shares this buffer,
including other threads.
Note: This function is not thread safe, because it shares a return buffer across all
threads, and many other functions in this library.
Example: This function is intended to be used in a fashion similar to the following
example:
long result = ptrace(request, pid, addr, data);
if (result < 0)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_ptrace(err, request, pid, addr, data));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_ptrace_or_die(3) function.
explain_message_ptrace
void explain_message_ptrace(char *message, int message_size, int request, pid_t pid, void
*addr, void *data);
The explain_message_ptrace function is used to obtain an explanation of an error returned
by the ptrace(2) system call. The least the message will contain is the value of
strerror(errno), but usually it will do much better, and indicate the underlying cause in
more detail.
The errno global variable will be used to obtain the error value to be decoded.
message The location in which to store the returned message. If a suitable message return
buffer is supplied, this function is thread safe.
message_size
The size in bytes of the location in which to store the returned message.
request The original request, exactly as passed to the ptrace(2) system call.
pid The original pid, exactly as passed to the ptrace(2) system call.
addr The original addr, exactly as passed to the ptrace(2) system call.
data The original data, exactly as passed to the ptrace(2) system call.
Example: This function is intended to be used in a fashion similar to the following
example:
long result = ptrace(request, pid, addr, data);
if (result < 0)
{
char message[3000];
explain_message_ptrace(message, sizeof(message), request, pid, addr, data);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_ptrace_or_die(3) function.
explain_message_errno_ptrace
void explain_message_errno_ptrace(char *message, int message_size, int errnum, int
request, pid_t pid, void *addr, void *data);
The explain_message_errno_ptrace function is used to obtain an explanation of an error
returned by the ptrace(2) system call. The least the message will contain is the value of
strerror(errno), but usually it will do much better, and indicate the underlying cause in
more detail.
message The location in which to store the returned message. If a suitable message return
buffer is supplied, this function is thread safe.
message_size
The size in bytes of the location in which to store the returned message.
errnum The error value to be decoded, usually obtained from the errno global variable
just before this function is called. This is necessary if you need to call any
code between the system call to be explained and this function, because many libc
functions will alter the value of errno.
request The original request, exactly as passed to the ptrace(2) system call.
pid The original pid, exactly as passed to the ptrace(2) system call.
addr The original addr, exactly as passed to the ptrace(2) system call.
data The original data, exactly as passed to the ptrace(2) system call.
Example: This function is intended to be used in a fashion similar to the following
example:
long result = ptrace(request, pid, addr, data);
if (result < 0)
{
int err = errno;
char message[3000];
explain_message_errno_ptrace(message, sizeof(message), err, request, pid, addr,
data);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the explain_ptrace_or_die(3) function.
SEE ALSO
ptrace(2)
process trace
explain_ptrace_or_die(3)
process trace and report errors
COPYRIGHT
libexplain version 1.4
Copyright (C) 2010 Peter Miller
explain_ptrace(3)